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tion, and the lower incisors are worn to needle-like points. The
two molars are excessively minute, and thus the always large gap
in the jaws is greatly exaggerated. It is suggested that this Hat
is an insect-eater, but nothing positive is known.

Sub-Fam. 4. Gerbillinae.—The Gerbilles form, another sub-
family, Gerbillinae, of the Muridae, or a family, according to some.
The best-known genus is Crertrillus, including the Gerbilles proper.
These animals are Old World in range, belonging to the three
regions of that part of the world. There are a large number of
species in the genus, over thirty. They have a Jerboa-like form,
with rather long hind-limbs and a long and hairy tail. Bat the
hind- as well as the fore-feet are five-toed. The molar teeth have
no trace of tubercles, but only transverse lamellae of enamel.

Fro. 236. — Gerbille.     Ger&ttlus ctegyptius.      x |.

The incisors are orange ; they are white in Dipits. Gerbillus
pyramidum is 90 mm. long, with a tail of 125 mm. The ears
are long, 13 mm. The tail has longer hairs at the tip.

Psammomys is in some respects different. The tail is shorter
than in Q&rbillus ; its length in an individual of 165 mm. was
130 mm. As in Gerbillus there are four pairs of teats, two
pectoral and two inguinal. This genus is exclusively Palaearctic
in range. Meriones has a range co- extensive with that of

Pachyuromys is an Ethiopian genus with a short tail. As
the generic name denotes, the tail is not only short but thick
and fleshy.
Bub-Fam. 5. Otomyinae. — The allied genera, Otoimys and
OTei'namySj are Ethiopian. Otowys itnisulcatus lias a tail shorter
than the body, the measurements of a female of this species being
137 mm. with a tail of 87 mm. The ear is long, whence the
name ; it measured in this specimen 2 0 mm.